Sub-annual I-129 environmental record of years 1956-2007 from an ice core in SE Dome Site, Greenland
Dr Angel Bautista VII1, Ms. S.J. Limlingan1, Ms. M. Toya, Dr. Y. Miyake3, Dr. K. Horiuchi4, Prof. H. Matsuzaki2, Dr. Y. Iizuka5
1Philippine Nuclear Research Institute (DOST-PNRI), , Philippines, 2Micro Analysis Laboratory Tandem Accelerator (MALT), The University of Tokyo, Tokyo, Japan, 3RIKEN Nishina Center for Accelerator-Based Science (RNC), Saitama, Japan, 4Graduate School of Science and Technology, Hirosaki University, Aomori, Japan, 5Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
Iodine-129 in ice cores can be used to reconstruct the historical impact of human nuclear activities transported through the atmosphere. Furthermore, this information can be used as an age marker to confirm ice core chronologies and as a tracer to better understand environmental processes. Here we show 129I levels in an ice core from SE-Dome, Greenland, for years 1956-2007 at a time resolution of ~ 4 months, the most detailed record to date.
Materials and Methods
The ice core analyzed in this study was drilled at the SE-Dome site (67.18°N, 36.37°W; 3,170 masl; Figure 1), 185 km north of Tasiilaq, Greenland. The total length of the ice core is 73.4 meters, which corresponds to the years 1956.1 to 2007.5. Subsampling at 0.5 m intervals, resulting in a total of 149 ice core samples. Iodine was extracted from the samples via CCl4 and NaNO2 solvent extraction followed by AgI precipitation and analysis for 129I and 127I via Accelerator Mass Spectrometry (AMS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in MALT, The University of Tokyo.
Results and Discussion
Results revealed 129I bomb peaks in 1959, 1962, and 1963, associated with tests performed by the former Soviet Union one year prior, in its Novaya Zemlya test site. All 129I bomb peaks were observed in winter (1958.9, 1962.1, and 1963.0), while tritium bomb peaks were observed in spring or summer (1959.3, 1963.4, and 1964.6). These results indicate that 129I and tritium bomb peaks can be used as annual and seasonal age markers for these years. Furthermore, 129I signals from nuclear fuel reprocessing and the Chernobyl Accident are recorded in the ice core. Comparisons with other published records of 129I in natural archives such as coral and sediment cores showed that 129I signals could also be used as common age markers and tracer for different types of records available in varying latitudes.
Iodine-129 record in the SE-Dome ice is the most detailed historical reconstruction of atmospheric 129I to date. Results show prominent seasonal bomb peaks that can be used as age markers. Common nuclear reprocessing and accident signals found in the SE-Dome ice core and other published records of varying archive types (e.g., coral and sediment cores) suggest the potential of using 129I to tie up and relate 129I records of different types of natural archives, which are exclusively available in varying latitudes in the world.
Angel Bautista VII is a chemist and the current Section Head of the Nuclear Materials Research Section of the Philippine Nuclear Research Institute (DOST-PNRI). His research interests include applications of AMS in studies on paleoenvironment, hydrology, climate change, disasters, archaeology, and the nuclear industry. Some of his ongoing research projects include I-129 in coral cores and seawater in the Philippines and in an ice-core from SE-Dome Greenland.